110 Prof. W. 0. McO. Lewis on the Relation of the 



whole force exerted upon it will be (/' — fyrne 2 )x. From 

 which it follows that 



4W 



The smaller /' is, i. e. the less tenacious the hold which a 

 molecule has upon one of its own electrons, the greater K 

 will be ; and this in turn should mean a large cohesion and 

 residual affinity. An interesting case in point is furnished 

 by liquid mercury. Its conducting power suggests that for 

 this substance /' is relatively small. Only a rough estimate 

 of it for mercury can be made. It is a very large quantity 

 however — possibly as great as 30,000 atmospheres/cm. 2 — 

 which is thus in agreement with the considerations put 

 forward. A complete experimental study of the p, v, T 

 relations of liquid mercury and vapour should be of con- 

 siderable importance from the standpoint of equations of 

 state. Further, attention may be drawn to the fact that the 

 conductivity of mercury (and other metals) increases as the 

 temperature falls, which possibly indicates a decrease in the 

 value of /', and consequently an increase in the value of K, 

 and therefore of the cohesion. That cohesion increases as 

 temperature falls is well known. As regards the intercon- 

 nexion between dielectric capacity and the continuity of state, 

 reference may be made to the measurements of Fversheim 

 (Ann. der Physih, viii. p. 539, 1902; ibid. xiii. p. 503, 1904), 

 who observed (in the case of the liquids examined by him, 

 notably in the case of ether) that the dielectric constant of 

 the liquid diminished regularly as the temperature was 

 raised, there being a linear relation between the two until 

 the critical region was reached, at which the K decreased 

 abruptly within small temperature limits and then con- 

 tinued to vary only slightly, i. e. it diminished linearly as 

 the temperature of the now gaseous system was still further 

 raised. (So sharp indeed is the change in K at the critical 

 temperature that the latter could be obtained from the KT 

 curve with very considerable accuracy.) 



Numerical values for the permeability //, of a number of 

 liquids may be obtained from Pascal's* determinations of 

 the susceptibility k by employing the relation yu,= l-f 47r£, 

 Pascal's values being given in electromagnetic units. As a 

 matter of fact, Pascal does not give the actual susceptibility 

 itself, but a quantity which he calls " the molecular suscepti- 

 bility," i. e. the product of the molecular weight into the 



* Pascal, Bull. Soc. Chim. France, [4] v. pp. 1060, 1110 (1909) ; ibid. 

 yii. pp. 17, 45 (1910). 



